The present invention relates to unique compositions comprising a dispersion of certain polydimethylsiloxanes in certain nonionic poloxamer surfactants. When added to water these dispersions are stable and are distinct from solutions, emulsions and microemulsions. These dispersions are referred to hereinafter as ultramulsions. These ultramulsions offer excellent utility in a broad range of coating applications, which are described in detail below.
The uniqueness and novelty of the ultramulsions of the invention are more readily appreciated when these compositions are compared to other dispersions such as emulsions and microemulsions.
When a system consists of a single liquid phase it is described as a solution. A system containing two or more liquid phases is described as a multiphase solution or emulsion.
According to Becher, an emulsion is an unstable heterogeneous system in which the diameters of the dispersed droplets in general exceed 1000 A. Becher P. in "Emulsions, Theory & Practice", (P. Becher, Ed.) page 2, Rheinhold, N.Y., 1965.
A more comprehensive definition of emulsion is advanced by Clayton: "An emulsion is a system containing two liquid phases, one of which is dispersed as globules in the other. The liquid which is broken up into globules is termed the dispersed or discontinuous phase, while the liquid surrounding the globules is known as the continuous phase or dispersing medium" Clayton, W., The Theory of Emulsions and Their Technical Treatment, 4th Ed. page 1, the Blakiston Co., Philadelphia, 1943. It is well accepted that, mechanical work is required to effect such an emulsion, see Bancroft W. D., J. Phy. Chem., 17: 501, (1913).
According to Prince, an emulsion may be defined as a dispersion of two (or more) mutually insoluble liquids, one in the other. Because of the surface tension forces at play between the two liquids, the dispersed phase consists of spherical droplets. Prince, L. M. Microemulsion Theory & Practice, pg. 2, Academic Press Inc., New York, N.Y. (1977). See also Prince, L. M. in Biological Horizons in Surface Science, pg. 361, Academic 1973,
Emulsions, are generally not stable and upon standing or after centrifuging tend to separate into two or more liquid layers.
The three definitions of emulsions set forth above share one common attribute, that is, mechanical work must be put into the emulsions described in order to disperse one liquid in the other in the form of droplets. This mechanical work can be in the form of agitation, homogenization, ultrasonication, etc.
In contrast, dispersions of very small droplet sizes which are formed spontaneously without the input of any mechanical work are called microemulsions. See Prince 1977, p. 3. Generally, two surfactants are used in forming microemulsions, i.e. a water soluble surfactant and a co-surfactant such as alcohol, where one phase of the microemulsion is generally water. Thus, dilution or adulteration of the dispersed phase by the co-solvent generally accompanies microemulsion formation. The ratio of surfactant to dispersed phase in microemulsions is much higher than that of emulsions. Microemulsions are further characterized as optically clear or opalescent and when spun in a laboratory centrifuge for 5 minutes at 100 G's, the dispersion remains stable and does not separate.
Thus, fine particle sizes, exceptional stability and rheological properties that can be easily adjusted, distinguish microemulsions from emulsions. Moreover, to late, no microemulsions have appeared in which one of the mutually insoluble liquids is not water. See Prince, page 34, (1977).